gccrs: expand: Add procmacro loading function

Add a function to load a shared object procmacro and retrieve the list
of available procedural macros.

gcc/rust/ChangeLog:

	* Make-lang.in: Add rust-proc-macro object to list.
	* expand/rust-proc-macro.cc: New file.
	* expand/rust-proc-macro.h: New file.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

gcc/rust/Make-lang.in

@@ -91,6 +91,7 @@ GRS_OBJS = \
 	rust/rust-derive.o \
 	rust/rust-derive-clone.o \
 	rust/rust-derive-copy.o \
+	rust/rust-proc-macro.o \
     rust/rust-macro-invoc-lexer.o \
     rust/rust-macro-substitute-ctx.o \
     rust/rust-macro-builtins.o \

gcc/rust/expand/rust-proc-macro.cc

@@ -0,0 +1,64 @@
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include "rust-diagnostics.h"
+#include "rust-proc-macro.h"
+#ifndef _WIN32
+#include <dlfcn.h>
+#endif
+
+namespace Rust {
+
+const std::string PROC_MACRO_DECL_PREFIX = "__gccrs_proc_macro_decls_";
+
+const ProcMacro::ProcmacroArray *
+load_macros_array (std::string path)
+{
+#ifndef _WIN32
+  void *handle = dlopen (path.c_str (), RTLD_LAZY | RTLD_LOCAL);
+  // We're leaking the handle since we can't ever unload it
+  if (!handle)
+    {
+      rust_debug ("Error whilst opening procedural macro: %s", dlerror ());
+      return nullptr;
+    }
+
+  // FIXME: Add CrateStableId handling, right now all versions may be loaded,
+  // even incompatible ones.
+  return *reinterpret_cast<const ProcMacro::ProcmacroArray **> (
+    dlsym (handle, PROC_MACRO_DECL_PREFIX.c_str ()));
+#else
+  rust_sorry_at (Location (),
+		 "Procedural macros are not yet supported on windows host");
+  gcc_unreachable ();
+#endif
+}
+
+const std::vector<ProcMacro::Procmacro>
+load_macros (std::string path)
+{
+  const ProcMacro::ProcmacroArray *array = load_macros_array (path);
+  // Did not load the proc macro
+  if (array == nullptr)
+    gcc_unreachable ();
+
+  rust_debug ("Found %lu procedural macros", array->length);
+
+  return std::vector<ProcMacro::Procmacro> (array->macros,
+					    array->macros + array->length);
+}
+
+} // namespace Rust

gcc/rust/expand/rust-proc-macro.h

@@ -0,0 +1,34 @@
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_PROC_MACRO_H
+#define RUST_PROC_MACRO_H
+
+#include "libproc_macro/proc_macro.h"
+
+namespace Rust {
+
+/**
+ * Load a procedural macro library and return a pointer to it's entrypoint.
+ *
+ * @param The path to the shared object file to load.
+ */
+const std::vector<ProcMacro::Procmacro>
+load_macros (std::string path);
+
+} // namespace Rust
+
+#endif /* ! RUST_PROC_MACRO_H */